Anorectal fistulae result from infection in the anal glands, which are located around the circumference of the distal anal canal that forms the anatomic landmark known as the dentate line. FIGS. 1 and 2 illustrate the typical anorectal fistulae 4 and 5 that commonly occur in man. The dentate line is shown at 1 of FIG. 1. Approximately 20-30 such glands are found in man. Infection in an anal gland usually results in an abscess, and the abscess then tracks through or around the sphincter muscles into the perianal skin, where it drains either spontaneously or surgically. The resulting tract is known as a fistula. The inner opening of the fistula, usually located at the dentate line, is known as the primary opening 2. The outer (external) opening, located in the perianal skin, is known as the secondary opening 3.
The path which these fistulae take, and their complexity, is very variable. A fistula may take a take a “straight line” path from the primary to the secondary opening, known as a simple fistula 4. Alternatively, the fistula may consist of multiple tracts ramifying from the internal (primary) opening and have multiple external (secondary) openings. This is known as a complex fistula 5.
The anatomic path which a fistula takes is classified according to its relationship to the anal sphincter muscles as shown in FIG. 1. The anal sphincter consists of two concentric bands of muscle, the inner or internal sphincter 6 and the outer or external anal sphincter 7. Fistulae which pass between the two concentric anal sphincters are known as inter-sphincteric fistulae 8. Those which pass through both internal and external sphincters are known as trans-sphincteric fistulae 9, and those which pass above both sphincters are called supra-sphincteric fistula 10. Fistulae resulting from Crohn's disease usually “ignore” these anatomic planes, and are known a “extra-anatomic” fistulae.
Many complex fistulae consist of multiple tracts, some blind-ending 11 and others leading to multiple external (secondary) openings 3. One of the most common complex fistulae is known as a horseshoe fistula 12, shown in FIG. 2. In this instance the infection starts in the anal gland (the primary opening) at the 12 o'clock location (with the patient in the prone position.) From this primary opening, fistulae pass bilaterally around the anal canal, in a circumferential manner. Multiple external (secondary) openings from a horseshoe fistula may occur anywhere around the periphery of the anal canal, resulting in a fistula tract with a characteristic horseshoe configuration 12.
Failed surgical treatment leads to potential complications such as incontinence and multiple complex fistula formation. Alternative methods and instruments have been described such as a coring-out instrument by U.S. Pat. No. 5,628,762 and U.S. Pat. No. 5,643,305; however, this tends to make the fistula wider and more difficult to close.
A prior art technique for treating a perianal fistulae was to make an incision adjacent the anus until the incision contacts the fistula and then excise the fistula from the anal tissue. This surgical procedure tends to sever the fibers of the anal sphincter, and may cause incontinence.
Other surgical treatment of fistulae traditionally involved passing a fistula probe through the tract of the fistula in a blind manner, using primarily only tactile sensation and experience to guide to probe. Having passed the probe through the fistula tract, the overlying tissue is surgically divided. This is known as a fistulotomy. Since a variable amount of sphincter muscle is divided during the procedure, fistulotomy also may result in impaired sphincter control, and even frank incontinence.
Alternatively, the fistula tract may be surgically drained by inserting a narrow diameter rubber drain through the tract. This is known as a seton (Greek, “thread”). The seton is passed through the fistula tract and tied as a loop around the contained tissue and left for several weeks or months, prior to definitive closure or sealing of the fistula. This procedure is usually performed to drain infection from the area, and to mature the fistula tract prior to a definitive closure procedure.
More recently, methods have evolved to inject sclerosant or sealant (collagen or fibrin glue) into the tract of the fistula to block the fistula. Such sealants are described in prior art, such as Rhee U.S. Pat. No. 5,752,974. One drawback with prior art is these glues are very viscous and clog the narrow-bore channels of the instrument as described in the current invention. Closure of a fistula using a sealant is usually performed as a two-stage procedure, including a first-stage seton placement and injection of the fibrin glue several weeks later. This allows residual infection to resolve and to allow the fistula tract to “mature” prior to injecting a sealant. If sealant or sclerosant were injected as a one-stage procedure, into an “unprepared” or infected fistula, this may cause a flare-up of the infection and even further abscess formation.
Whatever method is used, accurate identification of the entire course of the fistula tract usually is a prerequisite for successful surgery. Traditionally the course of the fistula tract is determined by using a long, thin, metal probe (a fistula probe). The probe is passed into the external opening and maneuvered in a blind manner through the fistula tract, and out through the internal (primary) opening. Since the probe is passed in a blind manner, there is a hazard of “missing” the actual fistula tract, and creating additional tracts. This results in creating further fistulae, “false passages”, incorrect location of the primary opening, and persistent or recurrent fistula formation. Surgical treatment of fistulae is often problematic, and recurrence rates of up 30% are described. Surgical fistulotomy of horseshoe fistulae results in an incontinence rate in up to 60% of patients, because of the need to divide sphincter muscle during surgery. Even use of fibrin glues is associated with high recurrence rates. There are reports of failure rates of over 80% in “blind” injection of sealant into a complex fistula, generally due to the presence of unrecognized tracts and infection within the fistula tract.
An important step in successful closure of a fistula tract is accurate identification and closure of the primary opening of the fistula. Once the internal opening has been accurately identified, effective closure is necessary to prevents recurrence.
This invention is concerned with an improved process of identifying the fistula tract, treating the tract and closing the tract.